Готові списки джерел за темами / Hypothèse du gradient de stress

Добірка наукової літератури з теми "Hypothèse du gradient de stress"

Автор: Grafiati

Опубліковано: 7 липня 2024

Оновлено: 7 липня 2024

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями

Оберіть тип джерела:

Ознайомтеся зі списками актуальних статей, книг, дисертацій, тез та інших наукових джерел на тему "Hypothèse du gradient de stress".

Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.

Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.

Статті в журналах з теми "Hypothèse du gradient de stress":

Dubos, Pierre Antoine, Quentin Hatte, Pascal Casari, Mireille Richard-Plouet, Pierre-Yves Jouan, Samuel Branchu, and Nadia Guitter. "Stress Gradient Determination in Anti-Corrosion Multilayer Coating." Materials Science Forum 941 (December 2018): 1632–38. http://dx.doi.org/10.4028/www.scientific.net/msf.941.1632.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

To reduce maintenance and to increase the corrosion protection and lifetime of maritimestructures while complying with environmental standards, multilayer coatings are applied to protectsteel sections. A new generation of hybrid sol-gel and/or HiPIMS Ni-based thin films appear toconstitute an efficient pre-treatment before the anti-corrosion paint application. However, increasingthe number of coatings and associated interfaces may lead to coating failure due to stresses inducedby the different deposition processes. Therefore developing smart models to assess the stressdistribution along these multilayers appears of significant importance. The well-known Stoneyformula cannot be used for multilayers and owing to the large dimensions of the object to be protected.To assess an easily measurable curvature after deposition, thin steel sheets are used but do not respectany more the Stoney hypotheses. So we set up an analytical thermo-elasto-plastic model to evaluatethe stresses induced by depositions in each layer. This model is based on the various thermalexpansion coefficients of every coat. After extrapolation along the complete thickness, combiningsol-gel and PVD deposition smoothens the stress difference between steel and paint. The shearstresses at interface seems thus to be reduced. The evolution of the stress difference between layerswith the imposed deflection can predict the mechanical strength and the interface failure. In order toevaluate the quality of the model, in-situ four-point bending in SEM was performed to study of theadhesion between the various layers. The results deduced from the model are in good agreement withSEM images.

López, Ramiro Pablo, Sergio Valdivia, Mónica L. Rivera, and Rodrigo S. Rios. "Co-occurrence Patterns along a Regional Aridity Gradient of the Subtropical Andes Do Not Support Stress Gradient Hypotheses." PLoS ONE 8, no. 3 (March 7, 2013): e58518. http://dx.doi.org/10.1371/journal.pone.0058518.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Bilek, Anastacia M., Kay C. Dee, and Donald P. Gaver. "Mechanisms of surface-tension-induced epithelial cell damage in a model of pulmonary airway reopening." Journal of Applied Physiology 94, no. 2 (February 1, 2003): 770–83. http://dx.doi.org/10.1152/japplphysiol.00764.2002.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Airway collapse and reopening due to mechanical ventilation exerts mechanical stress on airway walls and injures surfactant-compromised lungs. The reopening of a collapsed airway was modeled experimentally and computationally by the progression of a semi-infinite bubble in a narrow fluid-occluded channel. The extent of injury caused by bubble progression to pulmonary epithelial cells lining the channel was evaluated. Counterintuitively, cell damage increased with decreasing opening velocity. The presence of pulmonary surfactant, Infasurf, completely abated the injury. These results support the hypotheses that mechanical stresses associated with airway reopening injure pulmonary epithelial cells and that pulmonary surfactant protects the epithelium from this injury. Computational simulations identified the magnitudes of components of the stress cycle associated with airway reopening (shear stress, pressure, shear stress gradient, or pressure gradient) that may be injurious to the epithelial cells. By comparing these magnitudes to the observed damage, we conclude that the steep pressure gradient near the bubble front was the most likely cause of the observed cellular damage.

Franks, Steven J. "Competitive and facilitative interactions within and between two species of coastal dune perennials." Canadian Journal of Botany 81, no. 4 (April 1, 2003): 330–37. http://dx.doi.org/10.1139/b03-023.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

While there is substantial evidence for facilitation, the effects of such factors as stress and species identity on positive interactions remain controversial. At two coastal dune sites, I tested the hypotheses that facilitative interactions increase with increasing stress and disturbance along an environmental gradient and that facilitative interactions are stronger among heterospecific than among conspecific individuals. I transplanted Uniola paniculata and Iva imbricata plants into plots along with four conspecific neighbors, four heterospecific neighbors, or no neighbors across an environmental gradient. Neighbors increased target plant survival, suggesting facilitation, but biomass of targets was reduced by the presence of neighbors, suggesting competition. Unexpectedly, competition was greatest in the purportedly most stressful and disturbed zone. In this study, the outcome of neighbor interactions differed for biomass and survival and depended on position along the environmental gradient, but was independent of neighbor identity.Key words: competition, disturbance, facilitation, Iva imbricata, stress, Uniola paniculata.

Mehrabian, Amin, Dale E. Jamison, and Sorin Gabriel Teodorescu. "Geomechanics of Lost-Circulation Events and Wellbore-Strengthening Operations." SPE Journal 20, no. 06 (December 18, 2015): 1305–16. http://dx.doi.org/10.2118/174088-pa.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Summary Lost circulation, a major complication of drilling operations, is commonly treated by adding materials of various types, shapes, and particle-size distributions to the drilling mud. Generally known as wellbore strengthening, this technique often helps the operator to drill with higher mud gradients compared with that suggested by the conventional fracture-gradient or borehole-fracture-limit analysis. The underlying mechanisms through which a wellbore is strengthened, however, are not yet fully understood. This study explores these wellbore-strengthening mechanisms through an analytical solution to the related solid-mechanics model of the wellbore and its adjacent fractures. The provided solution is generic in that it takes into account the mechanical interaction of multiple fractures between one another and the wellbore under an arbitrary state of in-situ stress anisotropy. An additional generality in this solution arises from its unification and quantification of some solid-mechanics aspects of the previous hypotheses that have been published on the subject—i.e., stress cage, as well as the tip isolation and its effect on the fracture-propagation resistance. In relation to the stress-cage theory, the study investigates the wellbore-hoop-stress enhancement upon fracturing. The findings indicate that the induced hoop stress is significant at some regions near the wellbore, especially in the general vicinity of the fracture(s). However, given the strong dependency of wellbore stress on the mechanical and geometrical parameters of the problem, generalizing these results to the entire region around the wellbore may not always be trivial. The study also examines tip isolation, a common feature of fracture-closure and propagation-resistance hypotheses, through the analysis of partially reduced fracture pressures and a breakdown criterion, defined by the critical stress-intensity factor of the formation rock.

Humphrey, Charlotte, and Jonathan Elford. "Social class differences in infant mortality: the problem of competing hypotheses." Journal of Biosocial Science 20, no. 4 (October 1988): 497–504. http://dx.doi.org/10.1017/s0021932000017624.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

SummaryThere is no agreed explanation of the social class gradient in infant mortality. The longstanding debate continues between those who favour explanations based on natural or social selection and those who stress the influence of environmental circumstances. These explanations are often presented as competing hypotheses between which it is necessary to make an absolute choice. An article which takes this approach is critically examined. It is argued that such an approach may lead to erroneous conclusions, and may divert attention away from the primary task of understanding how to bring about further improvements in the survival of infants in the manual social classes.

Godivier, Josepha, Elizabeth A. Lawrence, Mengdi Wang, Chrissy L. Hammond, and Niamh C. Nowlan. "Compressive stress gradients direct mechanoregulation of anisotropic growth in the zebrafish jaw joint." PLOS Computational Biology 20, no. 2 (February 8, 2024): e1010940. http://dx.doi.org/10.1371/journal.pcbi.1010940.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Mechanical stimuli arising from fetal movements are critical factors underlying joint growth. Abnormal fetal movements negatively affect joint shape features with important implications for joint health, but the mechanisms by which mechanical forces from fetal movements influence joint growth are still unclear. In this research, we quantify zebrafish jaw joint growth in 3D in free-to-move and immobilised fish larvae between four and five days post fertilisation. We found that the main changes in size and shape in normally moving fish were in the ventrodorsal axis, while growth anisotropy was lost in the immobilised larvae. We next sought to determine the cell level activities underlying mechanoregulated growth anisotropy by tracking individual cells in the presence or absence of jaw movements, finding that the most dramatic changes in growth rates due to jaw immobility were in the ventrodorsal axis. Finally, we implemented mechanobiological simulations of joint growth with which we tested hypotheses relating specific mechanical stimuli to mechanoregulated growth anisotropy. Different types of mechanical stimulation were incorporated into the simulation to provide the mechanoregulated component of growth, in addition to the baseline (non-mechanoregulated) growth which occurs in the immobilised animals. We found that when average tissue stress over the opening and closing cycle of the joint was used as the stimulus for mechanoregulated growth, joint morphogenesis was not accurately predicted. Predictions were improved when using the stress gradients along the rudiment axes (i.e., the variation in magnitude of compression to magnitude of tension between local regions). However, the most accurate predictions were obtained when using the compressive stress gradients (i.e., the variation in compressive stress magnitude) along the rudiment axes. We conclude therefore that the dominant biophysical stimulus contributing to growth anisotropy during early joint development is the gradient of compressive stress experienced along the growth axes under cyclical loading.

Yakovenko, Sergey. "Modeling The Turbulent Scalar Fluxes In An Internal Wave Breaking Region In Stratified Flow With Obstacle." Siberian Journal of Physics 12, no. 1 (March 1, 2017): 79–90. http://dx.doi.org/10.54362/1818-7919-2017-12-1-79-90.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Based on averaging of the direct numerical simulation data obtained earlier, statistical moments are calculated in a turbulent patch arising after internal wave overturning in a flow with obstacle and stable stratification. Temporal evolution and spatial behavior of the turbulent-scalar-flux transport equation budget have been studied. A priori estimations of approximations for the pressure-scalar-gradient correlation and turbulent-diffusion processes in this equation have been carried out. The performed analysis is helpful to explore the turbulent patch in terms of statistical moments, and to verify closure hypotheses in turbulence models. It is shown that, in the global balance of the turbulent-scalar-flux equation, the mean-shear and buoyancy productions and the pressure-scalargradient correlation are roughly balanced, as for the shear Reynolds stress equation, and in contrast to the scalar variance and normal Reynolds stress equations. The algebraic turbulent-scalar-flux relations of the gradient diffusion type, as well as those derived in local-equilibrium and nonequilibrium assumptions are incorrect; therefore the use of the full turbulent-scalar-flux equation is justified.

Gutiérrez-Cánovas, Cayetano, David Sánchez-Fernández, Miguel Cañedo-Argüelles, Andrés Millán, Josefa Velasco, Raúl Acosta, Pau Fortuño, Neus Otero, Albert Soler, and Núria Bonada. "Do all roads lead to Rome? Exploring community trajectories in response to anthropogenic salinization and dilution of rivers." Philosophical Transactions of the Royal Society B: Biological Sciences 374, no. 1764 (December 3, 2018): 20180009. http://dx.doi.org/10.1098/rstb.2018.0009.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Abiotic stress shapes how communities assemble and support ecological functions. However, it remains unclear whether artificially increasing or decreasing stress levels would lead to communities assembling predictably along a single axis of variation or along multiple context-dependent trajectories of change. In response to stress intensity alterations, we hypothesize that a single trajectory of change occurs when trait-based assembly prevails, while multiple trajectories of change arise when dispersal-related processes modify colonization and trait-filtering dynamics. Here, we tested these hypotheses using aquatic macroinvertebrates from rivers exposed to gradients of natural salinity and artificially diluted or salinized ion contents. Our results showed that trait-filtering was important in driving community assembly in natural and diluted rivers, while dispersal-related processes seemed to play a relevant role in response to salinization. Salinized rivers showed novel communities with different trait composition, while natural and diluted communities exhibited similar taxonomic and trait compositional patterns along the conductivity gradient. Our findings suggest that the artificial modification of chemical stressors can result in different biological communities, depending on the direction of the change (salinization or dilution), with trait-filtering, and organism dispersal and colonization dynamics having differential roles in community assembly. The approach presented here provides both empirical and conceptual insights that can help in anticipating the ecological effects of global change, especially for those stressors with both natural and anthropogenic origins. This article is part of the theme issue ‘Salt in freshwaters: causes, ecological consequences and future prospects’.

Le, Aurora B., Abas Shkembi, Anna C. Sturgis, Anupon Tadee, Shawn G. Gibbs, and Richard L. Neitzel. "Effort–Reward Imbalance among a Sample of Formal US Solid Waste Workers." International Journal of Environmental Research and Public Health 19, no. 11 (June 1, 2022): 6791. http://dx.doi.org/10.3390/ijerph19116791.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Background: Solid waste workers are exposed to a plethora of occupational hazards and may also experience work-related stress. Our study had three specific hypotheses: (1) waste workers experience effort–reward imbalance (ERI) with high self-reported effort but low reward, (2) unionized workers experience greater ERI, and (3) workers with higher income have lower ERI. Methods: Waste workers from three solid waste sites in Michigan participated in this cross-sectional study. We characterized perceived work stress using the short-version ERI questionnaire. Descriptive statistics and linear tests for trend were assessed for each scale. Linear regression models were constructed to examine the relationship between structural factors of work stress and ERI. Gradient-boosted regression trees evaluated which factors of effort or reward best characterize workers’ stress. Results: Among 68 participants, 37% of workers reported high effort and low reward from work (ERI > 1). Constant pressure due to heavy workload was most indicative of ERI among the solid waste workers. Union workers experienced 79% times higher ERI than non-unionized workers, while no significant differences were observed by income, after adjusting for confounders. Conclusions: Organizational-level interventions, such as changes related to workload, consideration of fair compensation, and increased support from supervisors, can decrease work stress.

Більше джерел

Дисертації з теми "Hypothèse du gradient de stress":

Muhamed, Hassan. "Le rôle des interactions biotiques dans la régénération des chênes au niveau des communautés de forêts dunaires de la région Aquitaine (Sud-Ouest de la France)." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14576/document.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Bien que les interactions biotiques soient connues pour être déterminantes dans l’établissement des espèces, il est encore difficile de savoir quels facteurs sont impliqués dans l’équilibre entre interaction positive et interaction négative. Il est de fait difficile de savoir sous quelles conditions les interactions biotiques peuvent favoriser ou empêcher la régénération des espèces. Cette thèse vise à étudier le rôle des interactions biotiques d'arbustes avec des semis de chêne sur la régénération de trois espèces de chênes sur les forêts des dunes côtières d'Aquitaine en testant comment l’effet net de ces interactions varie le long d’un gradient d’aridité, sur deux étages de canopée et en fonction des stratégies fonctionnelles de trois espèces de Chêne dans un contexte de changement global. Ce travail a été effectué en utilisant deux approches, une approche descriptive en utilisant un patron de points répartis dans l’espace et une approche expérimentale en transplantant les semis cibles. Les résultats montrent que la variation spatiale, en terme d’interactions biotiques, est fortement corrélée avec la sévérité environnementale, avec des interactions entre jeunes pousses de chêne très sensibles aux sécheresses estivales et aux trouées dans les canopées. Les interactions testées étaient de nature facilitatrice dans les plots découverts dans les dunes sèches du nord de Soulac et tournaient à la compétition sous le couvert forestier dans les dunes plus humides du sud, à Seignosse. La nature des interactions était constant entre les stratégies fonctionnelles des espèces cibles de chêne. Les résultats de cette thèse montrent de manière générale une confirmation de la formulation originale du SGH qui prédit une augmentation de la facilitation en lien avec une augmentation de la sévérité environnementale et souligne le fait que la réduction du stress hydrique atmosphérique par des arbustes est nécessaire à la régénération des semis de chêne. Dans cette perspective, le sylviculteur doit conserver les arbustes du sous-étage, en particulier dans les trouées, afin de permettre une meilleure régénération des plants de chêne. Cette thèse met en évidence la nécessaire considération des interactions biotiques dans la régénération du chêne dans les actuelles sévères conditions climatiques et le rôle prépondérant de ces interactions dans la réponse aux changements climatiques futurs probables dans cette région Aquitaine
Although biotic interactions are known to be important determinants of species establishment, it is uncertain what factors determine the net balance between positive and negative interactions thus, under what conditions biotic interactions could enhance or impede species regeneration. Bien que les interactions biotiques soient connues pour être This thesis aims to study the role of biotic interactions of shrubs with oak seedlings for regeneration of three oak species on the Aquitaine coastal dune forests, by testing how the net effect of these interactions vary along aridity gradient, between two overstory canopies and in respect to the functional strategies of three oak species in the context of climate change. This was done by using two approaches, descriptive approach using spatial point pattern data and experimental approach by transplanting the target seedlings. The results show that the spatial variation in the nature of biotic interactions is strongly relate to environmental severity conditions, where the shrub-oak seedling interactions were very sensitive to increasing summer drought and canopy opening, the interactions strength was facilitative under gap plots in the dry northern dunes in Soulac and switch on competitive under forest plots in the wet southern dunes in Seignosse. The nature of the interactions was constant across the functional strategies of the targets species of oak. For the most part, results of this thesis show general support to the original formulation of SGH which predicts increasing facilitation with increasing severity and underscore the fact that atmospheric water stress reduction by shrubs is required for oak seedling regeneration. In this perspective, silviculturist should conserve understory shrubs, in particular in gaps, in order to allow a better regeneration niche of oak seedlings. This thesis highlights the importance of considering biotic interactions in oak regeneration under current harshness climatic conditions and with expectation to have an ambitious role in alleviation future climatic change consequence in this region

Rande, Hugo. "Effets du niveau de pollution métallique et des stratégies fonctionnelles sur les types d’effets en jeu dans les interactions entre plantes au niveau d’anciens sites miniers des Pyrénées." Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0032.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Les interactions entre plantes dans les milieux impactés par les métaux/métalloïdes dépendent de nombreux facteurs et sont encore très peu connues. Tout d’abord elles semblent dépendre du niveau de pollution métallique du milieu, mais aussi des stratégies fonctionnelles végétales des plantes interagissant. D’autre part, les plantes peuvent avoir plusieurs types d’effets sur leur environnement proche, effets s’exprimant à des temporalités différentes. En effet, les plantes ont un effet immédiat via leur canopée et racines sur les ressources et le microclimat à proximité. Aussi, au cours d’une saison de végétation, les plantes peuvent avoir des effets liés à la production de la litière et sa décomposition dans les sols sous leur canopée. A plus long-terme, lorsque ce cycle de production/décomposition est répété au fil des années, les plantes vont avoir un effet lié à la dynamique de la matière organique dans les sols. Dans cette thèse, notre objectif principal était de différencier ces effets, et de comprendre comment les stratégies fonctionnelles végétales des plantes pouvaient influencer les différents effets en jeu le long de gradients de pollution métallique. Nous avons étudié ces effets pendant trois années (entre 2020 et 2022) dans une ancienne vallée minière des Pyrénées Ariégeoises (Sentein, France). Dans cette zone d’étude, nous avons étudié les interactions entre plantes par des méthodes observationnelles et de transplantations de cibles avec contrôle de la présence de canopée et/ou de la litière des plantes, sur trois sites d’étude : un terril avec une pollution homogène et deux zones de résidus miniers avec des pollutions hétérogènes créant un gradient de pollution. Le long des gradients étudiés, les effets de canopée et de prélèvement racinaire ont suivi l’Hypothèse du Gradient de Stress, passant de la compétition à la facilitation avec l’augmentation de la pollution. Cette facilitation était d’autant plus forte que les espèces produisant l’effet sont dites « exploitatrices » (en lien avec l’exploitation des ressources du sol et Leaf Economic Spectrum), et bénéficiait le plus aux plantes les moins tolérantes aux métaux. Les effets positifs étaient surtout liés à l’amélioration des conditions microclimatiques lors d’épisodes chauds et secs en été. Concernant les effets liés à la production et décomposition des litières, des effets négatifs sur les plantes cibles ont été démontrés, suggérant des effets dits d’allélopathie élémentaire, et liés à la forte concentration en éléments métalliques dans les litières en décomposition. Ces effets négatifs de litière étaient maximums dans les milieux les moins pollués où les plantes métallophytes accumulatrices (qui ont des fortes teneurs en métaux dans leurs feuilles) et les plantes moins tolérantes aux métaux interagissaient. Ils étaient particulièrement marqués pour les cibles sensibles à la pollution métallique. Les résultats de cette thèse donnent des pistes potentielles pour utiliser la facilitation dans un cadre de phyto-management de milieux pollués par les métaux/métalloïdes, en prenant en compte explicitement les stratégies fonctionnelles végétales des plantes en interactions et le niveau de pollution en jeu. Des résultats obtenus pendant la canicule de 2022 nous donnent aussi une bonne vision des évolutions attendues des différents effets impliqués dans les interactions entre plantes dans les écosystèmes métallifères dans un contexte de changement climatique
Plant-plant interactions have been overlooked in metal/metalloids-impacted environments and are likely driven by several factors whose influence is barely known. First, plant-plant interactions depend on the level of metal pollution, but also on the functional plant strategies of the interacting plants. Furthermore, plants can have several type of effects on their immediate environment, acting at different timescales. Plants canopy and roots have an instantaneous influence on the microclimate and available resources in their immediate vicinity. Then, during a growing season, the production of litter and its decomposition beneath their canopy can influence soil chemical and physical properties. In the longer term, when this cycle of litter production/decomposition is repeated over the years, the dynamics of the organic matter will influence soil conditions even more. In this thesis, our main objective was to delineate these effects, and to understand how plant functional strategies can influence these various effects along metal pollution gradients. We studied these effects during three consecutive years (from 2020 to 2022) in a former mining valley in the French Pyrenees (Sentein, Ariège, France). In this area, we studied interactions between plants using observational and target transplantation methods controlling for the presence of plant canopy and/or plant litter, in three study sites: a slag heap with homogeneous pollution and two mine tailings areas with heterogeneous pollution creating a gradient of pollution. Along these gradients, short-term canopy and root-uptake effects followed the Stress Gradient Hypothesis, switching from competition to facilitation as pollution increased. This facilitation was stronger when the species producing the effect were acquisitive (in relation with soil resources and the Leaf Economic Spectrum), and benefits more the low metal-tolerant plants. These positive effects were mainly due to the improvement of micro-climatic conditions during hot and dry episodes in summer. Concerning the effects linked to litter production and decomposition, negative effects on target plants were found, suggesting the so-called “elemental allelopathic” effects, in relation with the high concentration of metallic elements in the decomposing litter. These negative litter effects were more important in the least polluted environments, where metal-accumulating metallophyte plants (which have high concentration of metals in their leaves) and less metal-tolerant plants interacts. They were particularly marked for targets sensitive to metal pollution. The results of this thesis give important perspectives regarding the use of facilitation for the phyto-management of metals/metalloids-polluted environments, given that the functional strategies of interacting plants and the level of pollution involved are explicitly considered. Additionnaly, the results obtained during the 2022 heatwave provide useful insights regarding the expected evolution of the different effects driving plant interactions in metalliferous ecosystems in a climate change context

Karkkainen, Ryan. "Stress-gradient failure theory for textile structural composites." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013704.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Hopkinson, David P. "Development of stress gradient enhanced piezoelectric composite unimorph actuators." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/16372.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Wolfe, Christopher Edward. "Damage accumulation in a gradient stress field in graphite/epoxy laminates." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/39360.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Bonello, Kenneth John. "Damage accumulation in graphite/epoxy laminates due to cyclic gradient stress fields." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/42999.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Batista, Daniela Miranda. "" Impacts of Warming on Freshwater Decomposers Along a Gradient of Cadmium Stress"." Master's thesis, Instituto de Ciências Biomédicas Abel Salazar, 2009. http://hdl.handle.net/10216/26239.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Ferry, Barbara Marie Céline. "Study of the stress gradient and the size effect in fretting fatigue." reponame:Repositório Institucional da UnB, 2017. http://repositorio.unb.br/handle/10482/31283.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Tese (doutorado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Mecânica, 2017.
Texto parcialmente liberado pelo autor. Conteúdo restrito: Capítulos 4 e 5.
Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2018-01-04T18:22:52Z No. of bitstreams: 1 2017_BarbaraMarieCélineFerry_PARCIAL.pdf: 3017479 bytes, checksum: b23c85c14a5f22650fc965f93bbbf89d (MD5)
Approved for entry into archive by Raquel Viana (raquelviana@bce.unb.br) on 2018-02-21T18:37:40Z (GMT) No. of bitstreams: 1 2017_BarbaraMarieCélineFerry_PARCIAL.pdf: 3017479 bytes, checksum: b23c85c14a5f22650fc965f93bbbf89d (MD5)
Made available in DSpace on 2018-02-21T18:37:40Z (GMT). No. of bitstreams: 1 2017_BarbaraMarieCélineFerry_PARCIAL.pdf: 3017479 bytes, checksum: b23c85c14a5f22650fc965f93bbbf89d (MD5) Previous issue date: 2018-02-20
A fadiga por fretting está relacionada com o processo de dano, localizado na fronteira de contato entre dois corpos submetidos a cargas de fadiga. A previsão desse fenômeno é de grande importância na análise, por exemplo, da vida de lâminas de discos de turbinas. Na fadiga por fretting, o campo de tensão é máximo na superfície de contato, sendo observado um alto gradiente de tensão sob essa superfície. A diferença de escala entre experimentos realizados em laboratórios e os sistemas industriais, motivaram, nessa pesquisa, uma investigação da influência do efeito de tamanho na previsão de vida em fadiga por fretting. Para quantificar o efeito do gradiente de tensão e o efeito de tamanho, diferentes testes foram realizados na Universidade de Brasília em um equipamento servo-hidráulico com dois atuadores especialmente desenvolvido para ensaios de fadiga por fretting. Os parâmetros de testes foram definidos de forma que induzissem diferentes gradientes de tensão nos corpos de prova e posteriormente foram ajustados de modo que o volume solicitado sob a região de contato fosse o mesmo. Após os ensaios, para investigar os mecanismos de dano, os corpos de prova foram analisados por meio de um microscópio confocal laser. Foi demostrado nesta tese que para a liga Ti-6Al-4V, uma abordagem não local, baseada no campo de velocidades em uma determinada área ao redor da região de contato consegue prover boas previsões de vida em fadiga por fretting. Uma análise da influência das forças de fadiga nos processos de iniciação e propagação de trincas foi realizada e indicaram que essas forças não podem ser negligenciadas. De fato, se cerca de 75% dos mecanismos de iniciação de trinca em fadiga por fretting são controlados por tensões de contato (cisalhantes e pressão de contato) a consideração das tensões normais possibilita realizar previsões de vida mais realistas. O estudo do efeito do tamanho foi dividido em duas fases. A primeira investigou a influência do volume solicitado, reduzindo a largura de contato, porém, o gradiente de tensão sob a área de contato e a área de dano dentro da zona de deslizamento foram mantidas constantes. Na segunda, mantendo os parâmetro experimentais σB,max/p0 e Q/fP constantes, a influência da área de dano no interior da zona de deslizamento foi isolada enquanto que a área de dano sob a zona de deslizamento foi reduzida. Os resultados experimentais foram analisados utilizando o critério de fadiga da Curva Modificada de Wöhler em conjunto com a Teoria da Distância Crítica. Foi observado que nenhum desses dois parâmetros influenciam significativamente a vida em fadiga por fretting. Assim, o termo “efeito de tamanho” deve ser analisado somente com base no efeito do gradiente.
Fretting fatigue refers to the damage process localized at the frontier of the contact between two contacting bodies subjected to fatigue loadings. The prediction of this phenomenon is of major importance in determining, for instance, the lifetime of fan’s disk. In the vicinity of the contact front, the stress field inherited from the contact loads is maximal at the surface and displays a strong gradient under the contact. The difference of scale between the laboratory’s experiments and the industrials’ system motivated the study of the impact of the size effect for the determination of the lifetimes. To quantify the effect of the stress gradient and of the size effect, tests were carried out on a two vertical-actuators fretting-fatigue rig at the University of Brasilia, with experimental conditions ensuring different stress gradient and later different volume solicited under the contact. Damage mechanisms were studied using post-mortem analysis with a confocal microscope on some contact elements tested. It was shown on this thesis, for a Ti-6Al-4V alloy, that a nonlocal approach, based on equivalent velocity field on a determined area around the contact, leads to good expectation for the determination of fretting fatigue lives. The influence of the bulk stress for the description of the fretting fatigue crack initiation and propagation was also determined and it appears that it could not be neglected for the determination of the crack initiation boundary. As a matter of fact, if around 75% of the crack initiation mechanism in fretting fatigue is controlled by the contact stresses, i.e. shear stress and contact pressure, the consideration of the normal stress allows to obtain more realistic prediction. The study of the size effect was divided into two phases. First the influence of the volume stressed was investigated by reducing the width of the contact but maintaining the stress gradient under the contact and the damaged area within the slip zone constant. Then, the influence of the damaged area within the slip zone was isolated by maintaining the experimental parameters, i.e. σB,max/p0 and Q/fP, constant while the damaged area under the slip zone was reduced. The experimental results were analysed by applying a fatigue criterion, the Modified Wöhler Curve Method, in conjunction with the Theory of the Critical Distance. It was found that none of these two parameters influences significantly the fretting fatigue lifetimes, and so the term ‘size effect’ usually referenced in the literature as a damaging effect should refer only to the gradient effect.

Batista, Daniela Miranda. "" Impacts of Warming on Freshwater Decomposers Along a Gradient of Cadmium Stress"." Dissertação, Instituto de Ciências Biomédicas Abel Salazar, 2009. http://hdl.handle.net/10216/26239.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Bellecave, Johan. "Stress Gradients In Fretting Fatigue." Thesis, Cachan, Ecole normale supérieure, 2015. http://www.theses.fr/2015DENS0036/document.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Cette thèse fait partie d’un programme de recherche international (IRG Cognac). Lancé par le motoriste SNECMA (groupe SAFRAN), ce projet regroupe l’ENS Cachan, UnB, ENSMA, CNRS, Snecma, Turbomeca et Messier Bugatti Dowti, et se concentre sur l’effet du gradient des contraintes sur endommagement par fretting fatigue. Le fretting-fatigue se réfère au processus d’endommagement localisés en bord de fuite entre deux corps en contact soumis à un chargement de fatigue. La maitrise de ce phénomène est d’une importance cruciale dans la détermination des durées de vie des disques de turbine. En bord de contact, le champ de contrainte hérité des forces de contact est maximal à la surface mais présente un fort gradient en s’éloignant du contact.Il a été montré dans cette thèse que pour l’alliage Ti-6AL-4V, les approches locales, basés sur le niveau de contrainte au points critiques ne sont pas applicable dans ces conditions. Une approche non locale, s’appuyant sur la théorie de la distance critique a donc été utilisée. En effet, des fissures courtes initiées au point critique peuvent propager jusqu’à rupture ou peuvent s’arrêter si la diminution des contraintes est suffisamment sévère. Une seconde difficulté réside dans la nature multiaxial et localement non proportionnel du chargement. Le fretting fatigue est généralement créé par la superposition d’un chargement de fatigue cyclique, d’une force normale à la surface souvent considérée constante, et d’une force cyclique tangentiel à la surface mais dont la fréquence peut être différente de celle de la fatigue.Les résultats des essais réalisés ont mis en évidence l’effet du gradient des contraintes sur la fissuration et ont étaient utilisés pour évaluer le potentiel de diffèrent critères pour le dimensionnement en fatigue des structures. La simulation du phénomène a en effet été réalisé en utilisant différente approches. La première s’appuie sur la Théorie de la distance critique et utilise un critère multiaxial. La seconde utilise l’amplitude du facteur d’intensité des contraintes, ΔK, pour prédire l’arrêt des fissures courtes. Finalement un récent modèle construit comme un critère de plasticité en pointe de fissure a été appliqué au problème de fretting fatigue. Ce critère a pour particularité de prendre en compte la contrainte T dans le développement asymptotique en pointe de fissure
This thesis is part of an international research program (IRG Cognac) initiated by the engine manufacturer SNECMA (SAFRAN group) involving ENS Cachan, UnB, ENSMA, CNRS, Snecma, Turbomeca et Messier Bugatti Dowty. The thesis focuses on the effect of a stress gradient in fretting fatigue. Fretting-fatigue refers to the damage process localized at the frontier of the contact between two contacting bodies subjected to fatigue loadings. The prediction of this phenomenon is of major importance in determining, for instance, the lifetime of fan's disc. In the vicinity of the contact front, the stress field inherited from the contact loads is maximal at the surface and displays a strong gradient from the surface. It was shown in this thesis, for a Ti-6AL-4V alloy, that local approaches, based on local stresses at the most critical point, are not appropriate to predict fretting fatigue lives. As a matter of fact, short cracks initiated at the most critical point may stop if the stress decay from the surface is strong enough or may continue their growth, up to the failure of the component, if the stress gradient from the surface is not string enough. A second difficulty is the multiaxial and non-proportional nature of the loading conditions. Fatigue-fretting stems from the combination of loads that have neither the same spatial distribution nor the same time-dependency. In fretting-fatigue tests, three loading components are considered, the fatigue loading of the component (cyclic), the normal part (assumed to be constant) and the in-plane part (cyclic) of the loads between the two contacting components. To quantify the effect of the stress gradient, tests were carried out on a fatigue testing contact bench developed at the University of Brasilia, with experimental conditions ensuring different stress gradient while keeping the maximal stress the same. Damage mechanisms were studied using post-mortem analysis and optical microscopy on the contact elements tested. The prediction of the fretting fatigue life was done using different approaches. The first one is based on the Critical Distance Method and a fatigue criterion. The second is based on a K-based short crack arrest method. Finally, a new criterion was proposed. This method considers a generalized von Mises yield criterion for the crack tip region and accounts for the T-stresses in the asymptotic LEFM development

Більше джерел

Книги з теми "Hypothèse du gradient de stress":

Pace-Asciak, Pia. The effects of magnitude and spatial gradient in wall shear stress on cell shape and gene expression. Ottawa: National Library of Canada, 2003.

Знайти повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Chang, Tony H. D. Effects of interfacial level gradient and channel slope on interfacial shear stress in near-horizontal stratified gas-liquid flows. Ottawa: National Library of Canada, 1993.

Знайти повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Patrick, Dunn, and United States. National Aeronautics and Space Administration., eds. An evaluation of a coupled microstructural approach for the analysis of functionally graded composites via the finite-element method. [Washington, DC: National Aeronautics and Space Administration, 1995.

Знайти повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

K, Binienda W., Kreider K, and NASA Glenn Research Center, eds. Analysis of a generally oriented crack in a functionally graded strip sandwiched between two homogeneous half planes. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.

Знайти повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

BONNE, Liver. Antics of Cats and Canines Coloring Book: Relieve Stress for Adults and Kids of Old Cats and Dogs, with Background Patterns in Gray Gradient. Independently Published, 2021.

Знайти повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Analysis of a generally oriented crack in a functionally graded strip sandwiched between two homogeneous half planes. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 1999.

Знайти повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Pierard, Luc A., and Lauro Cortigiani. Stress echocardiography: diagnostic and prognostic values and specific clinical subsets. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780198726012.003.0015.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Stress echocardiography is a widely used method for assessing coronary artery disease, due to its high diagnostic and prognostic value. While inducible ischaemia predicts an unfavourable outcome, its absence is associated with a low risk of future cardiac events. The method provides superior diagnostic and prognostic information than standard exercise electrocardiography and perfusion myocardial imaging in specific clinical subsets, such as women, hypertensive patients, and patients with left bundle branch block. Stress echocardiography allows effective risk assessment also in the diabetic population. The evaluation of coronary flow reserve of the left anterior descending artery by transthoracic Doppler adds diagnostic and prognostic information to that of standard stress test. Stress echocardiography is indicated in the cases when exercise electrocardiography is unfeasible, uninterpretable or gives ambiguous result, and when ischaemia during the test is frequently a false-positive response, as in hypertensive patients, women, and patients with left ventricular hypertrophy. Viability detection represents another application of stress echocardiography. The documentation of a large amount of viable myocardium predicts improved ejection fraction, reverse remodelling, and improved outcome following revascularization in patients with ischaemic cardiomyopathy. Moreover, stress echocardiography can aid significantly in clinical decision-making in patients with valvular heart disease through dynamic assessment of primary or secondary mitral regurgitation, transvalvular gradients, and pulmonary artery systolic pressure, as well as before vascular surgery due to the excellent negative predictive value. Finally, stress echocardiography allows effective risk stratification in patients with hypertrophic cardiomyopathy through evaluation of inducible ischaemia, coronary flow reserve, and intraventricular gradient.

Ryan, Kevin M. Prosodic Weight. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780198817949.001.0001.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Prosodic weight plays a central role in metrical systems, including stress, poetic meter, prosodic word minimality, and prosodic end-weight. In each, constraints regulate the interaction of weight and phonological strength. For example, in English, increasingly heavy syllables are increasingly likely to attract stress. Depending on the language and system, weight can be binary (heavy vs. light), higher n-ary (ternary, etc., but still categorical), or gradient (continuous on a ratio scale). Gradient weight is widely attested in stress, meter, and end-weight. The book emphasizes the typology and analysis of complex and gradient scales for weight as well as properties of weight that obtain universally across languages, systems, and scales. For example, across phenomena, greater sonority contributes to weight in the syllable rime but detracts from it in the onset. Scales are analyzed in terms of prominence mapping (varying stressability of elements) as opposed to moraic coercion. Prosodic minimality is analyzed in the context of larger prosodic constituents, revealing new issues. The book also offers the first detailed study of a minimum to which only certain final consonants contribute. Syllable weight in metrics is treated extensively, as complex weight in meter has been largely overlooked previously. Finally, prosodic end-weight is argued to be driven by phrasal stress, manifesting ultimately the same stress–weight interface as does word phonology. Among other things, this analysis captures that prosodic end-weight is confined to prosodically head-final contexts. Finally, complex and gradient weight brings questions concerning the phonetics-phonology interface into sharp focus.

Steigmann, David J. Concept of an elastic material. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780198567783.003.0001.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Chapter 1 describes the basic phenomenology and its abstraction in formulating the foundations of constitutive theory. Topics include the concept of deformation gradient and stress associated with the response of a neighborhood of amaterial point.

Kiss, Thomas, and Paolo Pelosi. Lung recruitment techniques in the ICU. Oxford University Press, 2016. http://dx.doi.org/10.1093/med/9780199600830.003.0120.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Lung recruitment manoeuvres (RMs) have been suggested as a means of homogenizing the lung structure and distribution of the mechanical stress across the lungs. Such effects can be achieved provided enough pressure is applied for enough time at the airways, and maintained if adequate levels of positive end-expiratory pressure (PEEP) are used. When RMs effectively open atelectatic tissue, shear stress, and cyclic collapse/reopening are importantly reduced. The lung response to RMs is mainly determined by cause and severity of lung injury, and the position of the lungs with respect to the gravity gradient. RMs can be performed in several different ways, the most relevant RMs in terms of clinical applicability are sustained inflation manoeuvres, high pressure controlled ventilation, incremental PEEP, and intermittent sighs.

Частини книг з теми "Hypothèse du gradient de stress":

Ohtsuka, Masaaki, Hideaki Matsuoka, Yukio Hirose, and Hitoshi Ishii. "The Influence of Stress Gradient on X-Ray Stress Measurement." In Advances in X-Ray Analysis, 463–70. Boston, MA: Springer US, 1995. http://dx.doi.org/10.1007/978-1-4615-1797-9_53.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Vermaat, J. E., and M. J. M. Hootsmans. "Periphyton dynamics in a temperature-light gradient." In Lake Veluwe, a Macrophyte-dominated System under Eutrophication Stress, 193–212. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-2032-6_12.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Börsig, Katharina, Ulrik Brandes, and Barna Pasztor. "Stochastic Gradient Descent Works Really Well for Stress Minimization." In Lecture Notes in Computer Science, 18–25. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-68766-3_2.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Rambal, S., and J. Leterme. "Changes in aboveground structure and resistances to water uptake in Quercus coccifera along a rainfall gradient." In Plant Response to Stress, 191–200. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-70868-8_11.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Khakalo, Sergei, Viacheslav Balobanov, and Jarkko Niiranen. "Isogeometric Static Analysis of Gradient-Elastic Plane Strain/Stress Problems." In Advanced Structured Materials, 229–35. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-31721-2_11.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Eremeyev, Victor A. "Antiplane Surface Wave Propagation Within the Stress Gradient Surface Elasticity." In Applied Wave Mathematics II, 29–37. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-29951-4_2.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Bhardwaj, Sachin, Arvind Keprate, and R. M. C. Ratnayake. "Residual Stress Prediction of Welded Joints Using Gradient Boosting Regression." In Communications in Computer and Information Science, 45–57. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-10525-8_4.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Vermaat, J. E., and M. J. M. Hootsmans. "Growth of Potamogeton pectinatus L. in a temperature-light gradient." In Lake Veluwe, a Macrophyte-dominated System under Eutrophication Stress, 40–61. Dordrecht: Springer Netherlands, 1994. http://dx.doi.org/10.1007/978-94-011-2032-6_5.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Yoshioka, Yasuo, Toshihiko Sasaki, and Makoto Kuramoto. "X-Ray Multiaxial Stress Analysis on Materials with Stress Gradient by Use of Cosψ Function." In Advances in X-Ray Analysis, 255–64. Boston, MA: Springer US, 1985. http://dx.doi.org/10.1007/978-1-4613-2471-3_38.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Kramer, Sharlotte. "Fracture Studies Combining Photoelasticity and Coherent Gradient Sensing for Stress Determination." In Experimental and Applied Mechanics, Volume 6, 655–76. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-9792-0_94.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Тези доповідей конференцій з теми "Hypothèse du gradient de stress":

Male´sys, Nicolas, Ludovic Vincent, and Franc¸ois Hild. "Probabilistic Modeling of Crack Networks in Thermal Fatigue." In ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61081.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

A probabilistic model is proposed to predict the formation and propagation of crack networks in thermal fatigue. It is based on a random distribution of sites where cracks form and on the shielding phenomenon corresponding to the relaxed stress field created around propagating cracks. The stress gradient that arises under a surface submitted to thermal shocks is accounted for as well as multiaxial stress states. Experiments using digital image correlation have been performed to introduce the hypotheses made herein, and others to identify the parameters of the crack density as a function of the stress range and the number of cycles. Simulations of the formation of crack networks in a heterogeneous biaxial state of stress are carried out. A good qualitative agreement is obtained with existing thermal fatigue experiments especially considering the effect of the stress range on the crack densities as well as on the distribution of crack sizes.

Antaluca, Eduard, Daniel Ne´lias, and Spiridon Cretu. "A Three-Dimensional Friction Model for Elastic-Plastic Contact With Tangential Loading: Application to Dented Surfaces." In ASME/STLE 2004 International Joint Tribology Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/trib2004-64331.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

A three-dimensional numerical model based on a semi-analytical method in the framework of small strains and small displacements with respect of Hertz’s hypotheses is presented for solving an elastic-plastic dented contact with friction. The calculation of surface deformations and pressure distribution, which is the most time consuming step during the elastic-plastic algorithm, is obtained using a method based on a variational principle with a Fast Fourier Transform (FFT) and a Conjugate Gradient Method (CGM). The method is fast enough to allow investigating the effect of a small size surface defect, here a debris denting, on the subsurface elastic-plastic stress state, requiring a fine mesh with around 106 surface grid points. Further, the FFT approach is also involved in the calculation of internal stress state. The plasticity model is based on an incremental load and Von Mises yield criterion. The effects of the contact pressure distribution and residual strain on the geometry of the contacting surfaces yield from the Betti’s reciprocal theorem with initial strain. The code is used to compute a few smooth and dented contacts, with several types of contact interfaces conditions, including frictionless and Coulomb friction. The effects of surface dents and friction on the contact pressure and subsurface stress field are presented and discussed.

Kenjeresˇ, S., K. Hanjalic´, and S. B. Gunarjo. "A T-RANS/VLES Approach to Indoor Climate Simulations." In ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31400.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

For accurate prediction of flow, scalar transport and wall heat and mass transfer in complex building space we propose a time-dependent RANS (T-RANS) approach which resolves in time and space the large-scale convective motion and associated deterministic eddy structure. The residual (“subscale”) turbulence is modeled by a single-point closure. The method can be regarded as Very Large Eddy Simulations (VLES) since the deterministic and modeled contribution to the turbulence moments are of the same order of magnitude. The modeled part becomes dominant in the near-wall regions where there are no large eddies and the proper choice of the subscale model is especially important for predicting wall friction and heat transfer. We use an ensemble-averaged 〈k〉 - 〈ε〉 - 〈θ2〉 algebraic stress/flux/concentration closure as the subscale model which can provide information about the stress and heat/species flux anisotropies. The method is especially advantageous for predicting flows driven or affected by thermal buoyancy, for which the conventional eddy-viscosity/diffusivity RANS models and gradient transport hypotheses are known to fail even in simple generic configurations. The approach was validated in a series of buoyancy-driven flows for which experimental, DNS and LES data are available. Examples of full-scale application include computational simulations of real occupied and furnished residential or office space in which the furniture elements and persons are treated as passive blocking elements. The simulation showed that the T-RANS approach can be used as a reliable tool for a variety of applications such as optimization of heating and ventilation system, building space insulation, indoor quality, safety measures related to smoke and fire spreading, as well as for accurate wall heat and mass transfer predictions.

Targove, J. D., and A. R. Murphy. "Coevaporated reduced-stress gradient-index films." In OSA Annual Meeting. Washington, D.C.: Optica Publishing Group, 1989. http://dx.doi.org/10.1364/oam.1989.mnn5.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

The coevaporation of LaF3 and BaF2 has been investigated as a means of reducing the large intrinsic tensile stress of fluoride films deposited at ambient temperature. CeF3 and BaF2 have previously been coevaporated from a single source for stress reduction.1 We have used coevaporation from separate sources for increased composition control and to allow separate deposition rate control for the two materials as a means of depositing gradient-index films. LaF3 was chosen as a UV transmissive material with chemical properties identical to CeF3. Refractive indices of the films decreased significantly. Gradient-index films with sinusoidal index profiles were then deposited by varying the BaF2 deposition rate while maintaining the LaF3 rate constant. This method thus allows gradient-index films with reduced stress to be deposited at wavelengths from the ultraviolet to the infrared.

Garg, Ajay, and Ravi Tetambe. "Elastic Stress Concentration Factors (Kt) by Stress Gradient Method Using FEA." In ASME 1996 Design Engineering Technical Conferences and Computers in Engineering Conference. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/96-detc/cie-1615.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Abstract The elastic stress concentration factor, Kt, is critical in determining the life of machines, especially in the case of notched components experiencing high cycle fatigue. This Kt is defined as the ratio of the maximum stress (σmax) at the notch to the nominal stress (σnom) in the region away from the notch effect. For simple geometries such as, plate with a hole, calculation of Kt from either closed form solution or from making simple but valid assumptions is possible [1,2]. However, for complex machine components such data is usually not available in the literature. Using Kt values from the simple geometries may lead to either over or under estimation of the real Kt for such complex geometries. Such error can then further lead to a substandard product or a product which is overdesigned and expensive. Present paper outlines a methodology for computing reasonably accurate elastic stress concentration factor, Kt, using finite element analysis (FEA) tool. The maximum stress (σmax) is readily available from the finite element analysis. The nominal stress (σnom) near the stress concentration is however can not be directly extracted from the FEA results. A novel approach of estimating reasonably accurate σnom is presented in this paper. This approach is based on selecting the correct path at the stress concentration region, post processing the stress and the stress gradient results along that path and identifying the cut of point where stress concentration effect begins to take place. This methodology is first validated using two examples with known Kt and later applied to a real world problem.

Lakhssassi, Ahmed, Mohammed Bougataya, Charbel Boustany, and Daniel Massicotte. "Thermal stress monitoring using gradient direction sensors." In 2008 Joint International IEEE Northeast Workshop on Circuits and Systems (NEWCAS) and TAISA Conference (NEWCAS-TAISA). IEEE, 2008. http://dx.doi.org/10.1109/newcas.2008.4606350.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Sedaghat-Pisheh, Hojr, Jung-Mu Kim, and Gabriel M. Rebeiz. "A Novel Stress-Gradient-Robust Metal-Contact Switch." In 2009 IEEE 22nd International Conference on Micro Electro Mechanical Systems (MEMS). IEEE, 2009. http://dx.doi.org/10.1109/memsys.2009.4805310.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Lu, Yuren, Erhong Li, Chunguang Xu, Xiaohui Zhang, and Xiaoxia Li. "Ultrasonic inspection method for residual stress gradient distribution." In 2021 IEEE Far East NDT New Technology & Application Forum (FENDT). IEEE, 2021. http://dx.doi.org/10.1109/fendt54151.2021.9749665.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

de Oliveira Miranda, Antonio Carlos, and Paulo Oliveira Júnior. "Use of Stress Gradient Factor for Welded Structures." In 27^th Brazilian Congress of Thermal Sciences and Engineering. ABCM, 2023. http://dx.doi.org/10.26678/abcm.cobem2023.cob2023-0514.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Tomkinson, Todd H., and Christopher E. Saxer. "Stress-Induced Birefringence in Gradient-Index Structures Fabricated by Ion-Exchange." In Gradient-Index Optical Imaging Systems. Washington, D.C.: Optica Publishing Group, 1994. http://dx.doi.org/10.1364/giois.1994.pd3.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

This paper examines an axial gradient-index (GRIN) glass sample produced by ion-exchange in the glass system: 0.704 SiO 2 + 0.044 Al 2 O 3 + ( 0.252 − χ ( z ) ) Na 2 O + χ ( z ) Li 2 O (where χ(z) represents the degree of exchange versus position, z), with the intention of determining χ(z) from a measurement of the index profile, n(z). Due to the ion-exchange conditions, the sample contains “frozen-in” stresses that strain the glass network, preventing it from obtaining its free expansion volume. The resulting volume change causes an additional birefringent index change. Therefore, when the index profile of the sample, n(z), is measured, it is necessary to take into account the sample’s birefringence to accurately determine the exchange profile, χ(z). The gradient’s index change, Δn(z), (where, Δn(z)=n(z)-nb, and nb is the base index), can be determined to accuracies reaching 0.03%. This paper shows that when frozen stresses are not taken into consideration, errors in determining χ(z) can reach 1.8%. However, it is shown that by also measuring the sample’s birefringence, determination of χ(z) may become more accurate.

Звіти організацій з теми "Hypothèse du gradient de stress":

Karkkainen, Ryan, and Bhavani Sankar. A Stress Gradient Failure Theory for Textile Structural Composites. Fort Belvoir, VA: Defense Technical Information Center, May 2006. http://dx.doi.org/10.21236/ada455158.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Hemrick, James Gordon, Edgar Lara-Curzio, and James King. Characterization of Min-K TE-1400 Thermal Insulation (Two-Year Gradient Stress Relaxation Testing Update). Office of Scientific and Technical Information (OSTI), September 2009. http://dx.doi.org/10.2172/969961.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Babuska, I., T. Strouboulis, C. S. Upadhyay, and S. K. Gangaraj. Study of Superconvergence by a Computer-Based Approach: Superconvergence of the Gradient of the Displacement, The Strain and Stress in Finite Element Solutions for Plane Elasticity. Fort Belvoir, VA: Defense Technical Information Center, February 1994. http://dx.doi.org/10.21236/ada279885.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Rogers, Caroline. A synthesis of coral reef research at Buck Island Reef National Monument and Salt River Bay National Historical Park and Ecological Preserve, St. Croix, U.S. Virgin Islands: 1961 to 2022. National Park Service, September 2022. http://dx.doi.org/10.36967/2294235.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

This synthesis focuses on the history of research on coral reefs within two U.S. National Park Service units in St. Croix, U.S. Virgin Islands: Buck Island Reef National Monument (from 1961 to 2022) and Salt River Bay National Historical Park and Ecological Preserve (from 1980 to 2022). Buck Island Reef National Monument (BUIS) is off the north shore of the island of St. Croix, in the U.S. Virgin Islands. Established in 1961 and expanded in 2001, it is under the jurisdiction of the National Park Service (NPS). Long-term monitoring programs maintained by the NPS and jointly by the University of the Virgin Islands (UVI) and the Virgin Islands Department of Planning and Natural Resources (VIDPNR) provide data on trends in living coral cover and specific coral species from 2000 and 2001, respectively. Disease, thermal stress (indicated by coral bleaching), and hurricanes reduced total coral cover periodically, but cover remained relatively stable from 2007 through the end of 2020. Salt River Bay National Historical Park and Ecological Preserve (SARI) is a national park on the north shore of the island of St. Croix, in the U.S. Virgin Islands. Established in 1992, it is co-managed by the NPS and the Government of the Virgin Islands. Long-term monitoring programs maintained by the NPS and by the UVI with the VIDPNR provide data on trends in living coral cover and individual coral species from 2011 and 2001, respectively. In spite of thermal stress (indicated by coral bleaching), disease, and hurricanes, total coral cover remained relatively stable through the end of 2020. This document also includes results from extensive investigations by the National Oceanic and Atmospheric Administration (NOAA) and from many individual projects including those based out of the underwater saturation habitats Hydrolab and Aquarius from 1977 to 1989, as well as studies from researchers at Fairleigh Dickinson University’s West Indies Laboratory. While not possible to review all of these in detail, this report highlights information considered useful to managers, and scientists planning future research. In 2021, a particularly virulent disease called stony coral tissue loss disease (SCTLD), first noted in 2014 in Florida, and then in 2019 in the U.S. Virgin Islands, started killing corals in BUIS and SARI with the different species showing a gradient of susceptibility. An exact cause or link between this disease and human actions has not been discovered to date. The losses associated with this disease have now exceeded those from any other stressors in these national parks.

Ray, Laura, Madeleine Jordan, Steven Arcone, Lynn Kaluzienski, Benjamin Walker, Peter Ortquist Koons, James Lever, and Gordon Hamilton. Velocity field in the McMurdo shear zone from annual ground penetrating radar imaging and crevasse matching. Engineer Research and Development Center (U.S.), December 2021. http://dx.doi.org/10.21079/11681/42623.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

The McMurdo shear zone (MSZ) is strip of heavily crevassed ice oriented in the south-north direction and moving northward. Previous airborne surveys revealed a chaotic crevasse structure superimposed on a set of expected crevasse orientations at 45 degrees to the south-north flow (due to shear stress mechanisms). The dynamics that produced this chaotic structure are poorly understood. Our purpose is to present our field methodology and provide field data that will enable validation of models of the MSZ evolution, and here, we present a method for deriving a local velocity field from ground penetrating radar (GPR) data towards that end. Maps of near-surface crevasses were derived from two annual GPR surveys of a 28 km² region of the MSZ using Eulerian sampling. Our robot-towed and GPS navigated GPR enabled a dense survey grid, with transects of the shear zone at 50 m spacing. Each survey comprised multiple crossings of long (> 1 km) crevasses that appear in echelon on the western and eastern boundaries of the shear zone, as well as two or more crossings of shorter crevasses in the more chaotic zone between the western and eastern boundaries. From these maps, we derived a local velocity field based on the year-to-year movement of the same crevasses. Our velocity field varies significantly from fields previously established using remote sensing and provides more detail than one concurrently derived from a 29-station GPS network. Rather than a simple velocity gradient expected for crevasses oriented approximately 45 degrees to flow direction, we find constant velocity contours oriented diagonally across the shear zone with a wavy fine structure. Although our survey is based on near-surface crevasses, similar crevassing found in marine ice at 160 m depth leads us to conclude that this surface velocity field may hold through the body of meteoric and marine ice. Our success with robot-towed GPR with GPS navigation suggests we may greatly increase our survey areas.

INVESTIGATION ON BEHAVIOR OF STEEL CABLES SUBJECT TO LOCALIZED FIRE IN LARGE-SPACE BUILDINGS. The Hong Kong Institute of Steel Construction, March 2024. http://dx.doi.org/10.18057/ijasc.2024.20.1.1.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

Анотація:

Pre-tensioned steel cable is a crucial load-bearing component of steel structure, the fire behavior of which affects the overall performance of the structure. However, it presently lacks research and fire safety design method to consider steel cable members subject to localized large-space building fire. In this paper, the mechanical behavior of normal steel strand cable and full-locked steel cable under large-space building fire is investigated, to provide guidance for the fire safety design of steel cable. Firstly, the numerical model of temperature field of steel cables subject to large-space building fire was established and verified with the test results. Secondly, based on the verified temperature field model, the sequential thermal-mechanical coupling numerical model was established to study the fire behavior of steel cable, including temperature field, temperature gradient, failure mechanism, internal force and contact stress. Thirdly, the numerical method was adopted for the parametric analysis on the fire resistance of steel cables, considering the effect of temperature-field model, non-uniform fire, load ratio and span of steel cable. The following conclusions are obtained: 1) The average temperature can be taken to simplify the transverse temperature field due to the small amplitude of transverse temperature gradient of steel cable section; 2) Because of the size effect of steel wire, the overall temperature of normal steel strand cable is higher than that of full-locked steel cable under the same conditions of same nominal diameter and fire conditions, and the damage occurs earlier than that of full-locked steel cable under fire.